This invention relates to a synchronizing device. In particular, the device is for use with automobile gear units, in which a shift sleeve is axially slidable along rams passing through the sleeve on an axis parallel to the sleeve. The ram ends in each case are fixed to a synchronizing ring, and means for limiting the shifting power is provided in the shift sleeve.
In standard synchronizing devices, the ram has a groove-shaped ring recess, into which at least one pressure piece, prestressed by a spring, meshes concentrically. The spring tension is designed so that the sliding sleeve must be displaced with a certain power in order to press the pressure piece through the ram into the sleeve body. If, then, the sliding sleeve is displaced axially with a certain power, then, at first, the entire assembly, consisting of the synchronizing ring, the rams and the sliding sleeve, is moved onto the assembly to be coupled. The corresponding synchronizing coupling is thereby engaged. It is not until after a pre-determined shifting power has been attained, which is adjusted so that the desired synchronizing is simultaneously attained, that the power limit on the ram is overcome and the sliding sleeve can again be displaced axially to thereby close the tooth or dog-clutch coupling.
In most of the standard synchronizing devices a pressure piece is attached in each case to a ram and, in turn, a pressure spring is attached to the pressure piece. The arrangement of pressure spring and pressure piece with regard to the ram is made in different variations. It is standard to provide spring and pressure pieces in a bored hole disposed radially in the sliding sleeve. Howver, in order to attain a corresponding spring tension, a large sliding sleeve is required. In addition it is standard to arrange the pressure pieces and the springs with their bored holes tangential to the circumferential direction of the sliding sleeve, so that, in order to get a higher locking power, two interlocking springs are used. Also, in order to be able to insert longer springs, the bored hole axis is shifted further inwardly from its tangential direction into the sleeve interior. The pressure pieces, however, are always arranged so that they act concentricly to the arm center.
It is known from DE-PS No. 885 354 that it is also possible to attach, in each cae, two pressure pieces which lie on the same axis to a ram. This is essentially tangential to their axes and passes through the ram center point, so that each ram is attached to its own pressure spring, which in turn is supported on the sleeve through screw-rams. Doubling the power is effected by a double arrangement wherein two pressure pieces and two springs are used.
In these standard synchronizing devices, in order to attain certain locking powers, many springs are needed. This in turn requires many bored holes, many parts, many working procedures, and much assembly time. The device is also of a higher weight, occupies larger construction space and provides correspondingly less reliability. The radial spring arrangement results in corresponding problems with large shaft diameters and small hub diameters. The plurality of springs and pressure pieces necessary for increased locking power causes a corresponding weakening of the sliding sleeve cross section and also a critical load of the springs. As a result there is a higher risk of breakage, in particular, in emergency situations and with large couplings.
It is an object of the invention to provide a synchronizing device in which, in a simple manner, a substantial increase in the locking power limit is obtained by using as few components and as simple an arrangement as possible. It is a further object to provide a device which is easily manufactured, has reduced weight and occupies reduced space and has a reduction in the installation time. In addition, the risk of breakage in emergency situations and in large couplings is also sought to be minimized.